msem-instigator

When Stygian Leviathan enters, target opponent loses life equal to the number of Curses attached to them and you gain that much life.

Menace (This creature can't be blocked except by two or more creatures.)
Civilized — Whenever Subjugator of Empires attacks, if you control an artifact, a creature, and an enchantment, each opponent discards a card, sacrifices a creature, and loses 3 life.

First strike, vigilance
When Subnautical Legionnaire enters, choose artifact, enchantment, or Merfolk. Exile target nonland permanent you don't control until you control no permanents of the chosen type.

Gain control of target noncreature permanent.
Coalesce {8}{U}{U} (You may cast this from your graveyard for {8}{U}{U}. If you do, it enters as a Horror creature after it resolves. Exile it if it would leave the battlefield or not resolve.)

Flying
Whenever a creature dealt damage by Subturgian Legionnaire this turn dies, create a 1/1 black Vampire creature token with lifelink.

When Suburban Runebrawler enters, exile target instant or sorcery card with mana value 2 or less from your graveyard.
Landfall — Once each turn, when a land you control enters, you may cast a copy of the exiled card without paying its mana cost.

Choose up to one creature. Return the rest to their owners' hands.

When Suitor of the Glade enters, put two +1/+1 counters on target creature you control. It gains vigilance until end of turn.

Vigilance, reach
Noncreature spells cost {2} more to cast.
Cycling {2} ({2}, Discard this card: Draw a card.)

When Sundering Arcanist enters, you may destroy target artifact or enchantment.
If you would draw a card, you may sacrifice a land and mill four cards instead. If you do, return Sundering Arcanist from your graveyard to your hand.

When Sunwright Scion enters, put a +1/+1 counter on each other creature you control.
At the beginning of each combat, you may have target creature with a +1/+1 counter on it gain your choice of vigilance, lifelink, or trample until end of turn.

You may sacrifice three Treasures rather than pay this spell's mana cost.
Flying, trample, haste

Whenever Supreme Mechanothurge or another artifact you control enters, up to one target artifact you control becomes a copy of another target artifact or creature you control, except it's an artifact in addition to its other types.

Target creature gains double strike and trample until end of turn. (Then exile this card. You may cast the creature later from exile.)

Flash
When Surreal Bakhtak enters, choose one —
• Destroy target tapped creature.
• Tap up to three target creatures.

Flying, prowess
Whenever Surveyor of Skies attacks, you may return a permanent you control to its owner's hand.

Primal {1}{G}{G} (During your turn, you may cast this spell for {1}{G}{G} instead of playing a land.)
When Swampedge Sentinel dies, return another creature card from your graveyard to your hand.

Lands target player controls don't untap during their controller's next untap step. Tap up to one target land that player controls.

When Swiftwheel Slayers enters, audition for red. (Create a 1/1 Construct Actor creature token, a Warrior Role giving 3/2 and trample, or a Wizard Role giving 2/2 and prowess. Roles replace older ones.)
Token creatures you control have haste.

(As this Discovery enters and after your draw step, add a progress counter. Stop after you've discovered.)
Archive 6 (As this enters, shuffle the top six cards of your main library into a new face up library. Sacrifice this after the archived library is empty.)
Draw a card from each of your libraries.
discover — When you draw the last card from the archived library, create a 4/4 blue Sphinx Wizard creature token with flying.

Lifelink (Damage dealt by this creature also causes you to gain that much life.)

Flying
When T'nege, Skyguard enters, exile another target creature you control until T'nege leaves the battlefield. If you do, exile target creature an opponent controls until T'nege leaves the battlefield.

Search your library for a card, put it into your hand, shuffle, then add three mana in any combination of colors.
{1}, Discard Tahli's Council: Add one mana of any color. Scry 1.

Spirited (When this creature enters, you may activate one of its activated abilities without paying its cost.)
{6}{R}: Takara Flameblade deals 4 damage to target creature. Activate only once each turn.

At the beginning of each upkeep, choose one that hasn't been chosen —
• Exile target tapped nonland permanent.
• Draw two cards, then discard a card.
• Return up to two target permanent cards from your graveyard to your hand.
• Exile Take the City, then return it to the battlefield under your control.